1. Field of Invention
The present invention relates to an amorphous alloy, whose strength is enhanced by means of dispersing fine crystalline particles.
2. Description of Related Arts
Heretofore, various amorphous aluminum-alloys are known in Japanese Unexamined Patent Publication No. 64-47,831. It is intended in every one of these aluminum-alloys to form a single amorphous phase so as to promote the strength-enhancement. It is proposed in Japanese Unexamined Patent Publication No. 2-59,139 that the crystalline particles be dispersed in the amorphous structure and hence enhance the strength. The amount of the crystalline particles dispersed is determined by the cooling speed and the composition of the mother alloy, specifically, the relationship between the amount of rare earth element(s) and the amount of Fe, Co and Ni. Desirably, the dispersion particles should have high strength and should have close inter-particle distance considering the theory of the law of mixtures. It is therefore desired that the inter-particle distance be shortened by controlling the cooling speed. Although, such controlling is not very effective for controlling the inter-particle distance, there are no other means than the cooling speed-control.
There is no clear and concrete theory for explaining the strengthening mechanism of the composite amorphous material, in which the crystalline particles are dispersed in the amorphous matrix. It seems however that the following requirements are given for the particles which greatly contribute to the enhancement: (1) the strength of dispersion particles is high; (2) good coherency is realized between the dispersion particles and the matrix; and, (3) inter-particle distance (.lambda.) is small.
The inter-particle distance (.lambda.) is greatly influenced by the following geometrical parameters and is expressed by: EQU .lambda.=(2/3)d(1-V.sub.p)/V.sub.p,
in which d is the diameter of a particle, and V.sub.p is the volume of a particle (M, GENSAMER; Trans. ASM, 36(1946), 30). It is believed that the .lambda. reduction is effective for enhancing the tensile strength. The yield strength .delta..sub.0.2 is expressed by: EQU .sup..delta. 0.2.varies.V.sub.p.sup.3/2 .multidot.d.sup.-1
A small (d) is therefore effective for enhancing the yield strength. There are two methods for decreasing the inter-particle distance (.lambda.), namely decreasing the diameter of a particle (d), and increasing the volume of a particle (V.sub.p). The latter method for increasing the volume of a particle incurs, however, reduction in elongation and hence impairment of toughness.